The present disclosure relates to solar photovoltaic (PV) panels systems and solar hot water systems, herein collectively referred to as solar panel systems. Specifically, the disclosure relates to an apparatus and system that compensates for thermal expansion and contraction of components in a solar panel system.
Solar panel systems, and in particular, rooftop mounted solar panel systems are generally susceptible to the weather. This includes seasonal and daily temperature changes. For example, in a dry or desert climate, temperatures may vary between day and night by as much as 60° F. (33.3° C.). In some regions of the United States, temperatures can vary seasonally by over 150° F. (83.3° C.). These temperature variations can cause significant expansion and contraction to solar PV panels or solar hot thermal panels, collectively referred to herein as solar panels, and to their mounting rails. This is particularly apparent when the solar panels are mounted in a continuous run of 100 ft. (30.48 m) to 300 ft. (91.44 m) or more. For example, a solar panel installation with a 100 ft. (30.48 m) run of aluminum mounting rail can expand or contract approximately 1.5 in (0.038 m) over a seasonal variation of 100° F. (54.5° C.) typical in many regions of the world. For a 300 ft. (91.44 m) run of solar panels that expansion and contraction would be approximately 4.5 in (0.114 m) over the same seasonal 100° F. (54.5° C.) temperature variation.
This expansion and contraction of solar panel system components can be challenging for concrete, and steel roof mounted solar panel system and can be particularly challenging for solar panel installations on wood sheathed roofs. For example, wood thermally expands 17%-22% of what aluminum would expand over the same given change in temperature. For the above mentioned 100° F. (54.5° C.) seasonal variation, a 100 ft. (30.48 m) length of wooden roof can expand as little as 0.25 in (0.0196 m) compared with 1.5 inches (0.038 m) for same length of the aluminum rail or back-to-back aluminum framed solar panels. This difference is enough to cause significant stress and possible buckling of components, including detachment of the mounting bolts, within the solar mounting system.
Attempts to solve this problem include creating thermal breaks or gaps between the a set length of rail, typically every 40 ft. (12.19 m) or 100 ft. (30.48 m) where there is a preset gap between both rail and solar panels on either side of the thermal break. This arrangement can be undesirable. For example, this arrangement dictates the structurally layout of the solar panels within the system making system planning challenging. It can also create gaps across solar panel arrays that may be aesthetically undesirable.